The present invention relates generally to oil pumps and more particularly to an engine oil pump device capable of reserving oil therewithin even when the engine is stopped.
An example of oil pumps being used at present in engines such as vertical shaft engines is disclosed in Japanese Utility Model Appln. Laid-Open Publn. No. 192585/1986. The pump is a rotary pump of the so-called internal-gear, one-tooth difference type. In the oil pump, as installed, an internal-gear-impeller assembly or a pumping mechanism is horizontally supported on a vertical pump shaft. The pumping mechanism is disposed above the oil surface of the oil pan in some cases. In such a case, if the engine is stopped for a long period, the oil within the pump chambers will flow under the force of gravity toward the oil pan side. Then, when the engine is again started, the lubrication of the clearance between the upper and lower surfaces of the pumping mechanism and the pump housing will become poor. Furthermore, it will become impossible to rely fully on the sealing effect of these clearance.
As a consequence, seizing of the pumping mechanism is apt to occur. Another undesirable consequence is defective suction of oil at the next starting of the engine. Thus, the engine performance and its durability drop.
Furthermore, similar trouble and failures occur also when ample oil is not adhering to the above mentioned clearance at the time of initial assembly and disassembly and reassembly for maintenance.